The present invention relates to an improved electrical connector for semirigid coaxial cable and, more particularly, to a connector constructed to eliminate an RF choking phenomenon associated with connectors crimped to semirigid coaxial cable.
A typical semirigid coaxial cable includes an inner electrical conductor, a surrounding dielectric and a semirigid outer conductor peripherally enveloping the dielectric. Although such cables are generally provided in standard diametric sizes, commonly practiced manufacturing techniques result in diametric variations along the cable length such that, for purposes of standardization, this cable parameter is often specified in terms of nominal size--the magnitude of acceptable variations from nominal size being known.
Terminating electrical connectors for semirigid coaxial cable must be correspondingly provided with inside diameters dimensioned to accomodate the manufacturing variations permissible for cable of a given nominal size. The combination of required connector and cable tolerances yields a small but variable annular gap between the outer diameter of the cable and the interior diameter of the connector. In utilizing known connectors that are soldered to the cable, the solder flows into and fills the radial gap to create an electrically and mechanically stable structure. However, in solderless connectors--i.e. those that are crimped or similarly mechanically secured to the semirigid outer conductor of the cable--the annular gap is not filled and its presence, particularly at the interface with a mating connector or jack, produces a so-called choke effect. In essence, the gap acts as a microwave cavity which resonates at frequencies dependent upon its dimensions; the result is a sharp increase in the voltage standing wave ratio (VSWR) at some particular frequency.
Referring, by way of example, to FIG. 1, a prior art crimp-type connector generally designated 10 is illustrated in secured relation about a semirigid coaxial cable 12. Cable 12 comprises an inner conductor 14 surrounded by a dielectric 16 and, in turn, by a semirigid outer conductor 18 of a minimum manufactured diameter. The elongated connector body 20 is crimped about cable 12 at the rear or distal end of the body. A threaded coupling nut 22 disposed for free axial rotation about the proximal end of body 20 is coupled to the body by a C-ring 24 or the like. An annular gasket 26 provides a cushioned seal when connector 10 is coupled or secured to a mating connector (not shown) in conventional fashion to electrically connect cable 12 to another cable or to a terminal device or the like.
Clearly visible in FIG. 1 is the aforementioned annular gap 28 lying between the outer periphery of semirigid outer cable conductor 18 and the interior peripheral wall 30 at the proximal end of connector body 20. Clearly, even with careful machining of the proximal bore in body 20 the dimensions of gap 28 will vary from cable to cable in accordance with corresponding variations in the cable outer diameter. In addition, the dimensions of gap 28 are altered when the cable is stressed or flexed in the vicinity of connector 10, causing the VSWR peaks to be evanescent in nature. The points of contact between connector body surface 30 and the periphery of semirigid outer cable conductor 18 shift back and forth with stress on or flexing of the cable causing transitory impedance disturbances and reflective losses at the interface between mated connectors.
It is accordingly the desideratum of the present invention to provide an improved connector that, when conventionally crimped or otherwise attached about semirigid coaxial cable, provides a secure mechanical connection to the cable in the area of the mated connection interface.
It is a further object of the invention to provide an improved connector for semirigid coaxial cable that prevents the formation of a gap between the outer periphery of the cable and the interior surface of the connector body at the proximal end or mated connection interface of the connector.
It is another object of the invention to provide an improved connector for semirigid coaxial cable that eliminates the so-called choke effect produced when conventional crimp-type connectors are attached to semirigid cable.
It is a still further object of the invention to provide an improved connector for semirigid coaxial cable that satisfies the foregoing objects while remaining electrically and mechanically compatible with existing conventional mating connectors.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention for which reference should be made to the appended claims